At the moment content authors don't seem to be able to filter documents by a content relationship in the dashboard.
This would be a nice feature to have for maintenance of a suite of content. The main reason I was trying to do this was to see what the consequences of deleting a document would be and how many potential dead links I would leave behind to be fixed.
Thanks for the valuable suggestion. This is really nice feedback. I will pass your feedback along to our @features-team and let you know if I have any updates.
For the moment, you can try to filter documents by using the tag system. Please find more details here.